What I said before is the legal-eagle answer.Thanks, had some sellors say yes i can but was not feeling that truthful. Appreciate it !!!
Typically "Complete Lower" includes whatever receiver extension and buttstock they put on it. If the lower is built as a rifle, originally, then it can not be built as a pistol. If you do, you will be assembling a 'firearm made from a rifle' and if that barrel is under 16" you're afoul of NFA problems.
To build a pistol from an AR receiver, you have to start with a lower that has never been built as a rifle, before.
Thanks for the clarification. I thought it was the buttstock that made it the rifle, rather than the barrel. For instance: http://www.franklinarmory.com/XO-26_Letter__c_.pdf seems to indicate that a handgun that's over 26" OAL would be a "firearm" so long as it had no buttstock, and makes no mention of a /maximum/ barrel length, and as we see in the letter you link, there is no restriction on pistol barrel length, so conceivably it could have a 16+ " barrel and still be simply a "firearm" because it lacks a buttstock.This is not correct. Even if it had a rifle buffer tube on it, as long as it has never been BARRELED as a rifle, it may be built into a pistol. I would simply make sure that the FFL logged it in as other firearm, and showed it on the 4473 as a receiver.
Here is the ATF letter that supports this position.
http://www.guntrustlawyer.com/ATF%20Response%20-%20AFG%20on%20AR%20Pistol.pdf
I guess maybe it's /both/ the buttstock and the barrel length that makes a rifle?